Avoiding tarmac

Ordnance Survey has an article on longest linear British walks without crossing any roads.... pretty sure I won't be trying the route, but in case anyone is really REALLY averse to walking on tarmac, here it is :

I had a feeling it would be somewhere crossing the Forest of Atholl or close by. That is the area I immediately think of as being almost devoid of any human construction. Somewhere around there is the furthest crow flies distance it is possible to stand from any public road on the mainland.

At first glance it looks awful. A bit of effort would show a human, manageable winding line to negotiate natural obstacles, hillsides, streams, etc. Which would also be farther. More far. A longer distance. There's a job for someone. Didn't whatsisface do the watershed?